package com.yuanxiao.sqlSession;

import com.yuanxiao.pojo.Configuration;
import com.yuanxiao.pojo.MappedStatement;

import java.lang.reflect.*;
import java.util.List;

public class DefaultSqlSession implements SqlSession {
    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementId, Object... params) throws Exception {
        //将要去完成对simpleExecutor里的query方法的调用
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        List<Object> query = simpleExecutor.query(configuration, mappedStatement, params);
        return (List<E>) query;
    }

    @Override
    public <T> T selectOne(String statementId, Object... params) throws Exception {
        List<Object> objects = selectList(statementId, params);
        if(objects.size() ==1){
            return (T) objects.get(0);
        }else {
            throw new RuntimeException("查询结果为空或者返回结果过多");
        }
    }

    @Override
    public void execute(String statementId, Object... params) throws Exception {
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        simpleExecutor.execute(configuration, mappedStatement, params);
    }

    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        //使用JDK动态代理来为dao接口生成代理对象条件，并返回
        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                //底层还是取执行JDBC代码 根据不同情况调用selectOne或者selectList
                //准备参数 1 statementId sql语句的唯一标识，namesapce.id== 接口权限定名.方法名
                //方法名 findAll
                String methodName= method.getName();
                //全限定名
                String className = method.getDeclaringClass().getName();//获取该方法所在的类的字节码对象
                String statementId=className+"."+methodName;
                //准备参数2 params=args
                //获取被调用方法的返回值类型
                MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
                String sqlType = mappedStatement.getSqlType();
                if("select".equals(sqlType)){
                    Type genericReturnType = method.getGenericReturnType();
                    //判断是否进行了泛型类型
                    if (genericReturnType instanceof ParameterizedType){
                        return selectList(statementId, args);
                    }
                    return selectOne(statementId, args);
                }else {
                    execute(statementId,args);
                    return null;
                }



            }
        });
        return (T) proxyInstance;
    }
}
